Former U.S. security officials warned on Tuesday that Russia may use cyber warfare against the U.S. and Ukraine if tensions between the two sides continue to escalate.

“If we move to the heavy sanctions, the sectoral sanctions ... the Russians are going to strike back in some way,” said former U.S. counterterrorism czar Richard Clarke, who spoke on a panel about cybersecurity at the Milken Institute Global Conference in Beverly Hills, California.

“[Russians] can’t strike back … [with] economic sanctions that would have the same kind of effect. What they can do … is a cyberattack to get back at us … attacking our financial institutions in ways that we’ll never be able to prove it was them but we’ll suffer the pain.”

Former Defense Secretary Leon Panetta, who also spoke on the panel, said the U.S. should work with Ukraine to prepare a defense against this potential cyberattack.

“We’ve seen [Russia] use [cyber warfare] in Georgia. We’ve seen some elements of that being used in Crimea,” Panetta said. “If [Russia] has an attack plan, a cyber element is very much a part of that attack plan. It takes down communications, takes down missile systems, takes down the counter attack…”

Panetta went on to call cyberattacks the "battleground of the future," and said that Russia is second only to the U.S. in its cyber capability.

“The sophistication of what’s being developed today has the ability to create a lot of hell,” Panetta said. “[Our] adversaries are looking at computer systems that run our electrical grid … chemical systems … water systems … transportation systems … financial systems.”

The three panelists noted that cyberattacks already frequently happen to U.S companies. Earlier this year, hackers stole the personal and financial data of 110 million Target shoppers, revealing the vulnerability of large companies' security systems. A study last year by the Ponemon Institute, a private security research group, looked at 60 companies across various sectors and found that they faced an average of two successful attacks each week, an 18 percent increase from the institute’s study in 2012.

Earlier this month, the Securities and Exchange Commission announced that it will be investigating more than 50 Wall Street firms to determine if their cybersecurity strategies are secure. Clarke said he believes the government will continue to take similar measures to require that public and private companies share information about their cybersecurity strategies.